The present invention relates generally to the field of forming shaped absorbent pad structures from an absorbent web, the pads being suitable for use in disposable absorbent articles such as diapers, child""s training pants, feminine care articles, incontinence articles, swim pants, and the like.
Many types of disposable consumer products such as diapers, training pants, feminine care articles, incontinence articles, and the like, utilize an absorbent pad structure for absorbing and wicking away bodily fluids. The absorbent pads are conventionally formed from an absorbent web, typically a non-woven fibrous web material formed by known techniques. For example, the absorbent web may be formed by employing conventional air forming techniques wherein fibers and typically a superabsorbent material are mixed and entrained in an air stream and then directed onto a forming surface to form the web. The absorbent web may then be directed for further processing and assembly with other components to produce a final absorbent product.
With another conventional technique, preformed absorbent web sheets or layers are delivered into a manufacturing line from a preformed supply, such as a supply roll. The sheets or layers have been separated into adjacent strips having various configurations of repeat pattern xe2x80x9cnestedxe2x80x9d shapes wherein the shape of one strip is substantially nested with the shape of at least one immediately adjacent strip.
Absorbent web material formed on a remote base machine and supplied to the manufacturing line from a roll or other supply form generally has a significant cost disadvantage as compared to air laid webs formed on a converting machine. With the air laid web, the trim waste can be immediately recycled by returning the waste to the upstream fiberizing equipment. On the other hand, with the roll material, the geographical separation of the base machine makes recycling of the trim waste impractical and often cost prohibitive. In this regard, the nesting feature mentioned above has been desirable to reduce the amount of waste that is generated from the supply (roll) of absorbent web
It has been recognized that particular nested strip shapes can be more readily adapted to high-speed manufacturing processes. The more easily processed strip-shapes have a repeat pattern that is substantially symmetrical with respect to their longitudinal dimension, the shapes being arranged longitudinally in the machine-direction of the web. With such longitudinally-symmetric nested patterns, a single cycle of the repeat pattern provides an individual web segment wherein the shape of a first lengthwise half portion of the segment substantially matches the shape of the longitudinally opposed other half portion. However, such longitudinally symmetric pads have been shown, in certain application, to be less desirable from an end product fit, comfort, and performance aspects.
As a result, it has been desirable to construct absorbent pads from web segments that are longitudinally-asymmetric. With such a construction, the resulting pads may provide improved product fit, comfort, and performance. However, the dividing of an absorbent web into strips having a nested pattern shape of longitudinally asymmetric segments generates a significant amount of trim waste, particularly along the machine-direction sides of the absorbent web.
Examples of suggestions in the art to reduce trim waste may be found, for example, in U.S. Pat. Nos. 5,587,437; 5,695,846; 5,580,411; 4,862,574; EP 0 539 032; and EP 0 670 153.
The present invention provides a method for producing longitudinally asymmetric nested pad structures in a continuous absorbent web wherein there is virtually zero waste of the web material.
Objects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.
The present invention provides an improved method for making absorbent pads having a longitudinally asymmetric shape. Such pads may be used in various applications of disposable consumer absorbent articles, such as diapers, child""s training pants, feminine care articles, incontinence articles, swim pants, and the like. The pads are longitudinally asymmetric in that the back portion has a different shape or configuration as compared to the crotch or front portion of the pad. As mentioned, longitudinally asymmetric pads of this type have proven to be superior with respect to product fit, comfort, and performance as compared to longitudinally symmetric pads. The present method provides a technique for mass producing such pads from a continuous strip of absorbent web material in a manner so that there is virtually zero waste of the web material.
In accordance with one embodiment of the present method, the absorbent web material is delivered in the form of a continuous strip or series of adjacent strips, for example from a supply roll, in a machine-direction flow. In other words, the parallel sides of the strip of material lie in the machine-direction. The absorbent web material is cut in a cross-direction to form a repeating nested pattern of cross-directional and generally identically shaped pads. The pads are nested in that any two adjacent pads forming a nested pair are oriented in longitudinally opposite directions in the cross-direction of the absorbent web. In other words, the longitudinal centerline of the pads lies generally perpendicular to the machine-direction of the web material.
The pads are defined by cross-directional cuts such that the crotch portion of one pad is oriented towards the back portions of immediately adjacent pads. Adjacent nested pads share common defining cut lines such that there is no wastage of absorbent material between the nested pads. Each pad is longitudinally asymmetric with respect to the crotch and back portions. For example, in one particular embodiment, the back portion of the pads includes ears that define the widest width of the pad, with a smaller width crotch section extending longitudinally from the ears and back portion.
In one particular embodiment, the individual absorbent pads are defined across the strip of absorbent web material such that each pad has a longitudinal length that is less than the cross-directional width of the web material. In this embodiment, however, a nested pair of the absorbent pads has a combined nested longitudinal length that is equal to the cross-directional width of the web material. For example, according to this particular embodiment, the absorbent pads may be generally T-shaped with a back ear portion having a width measured in the machine-direction that is about twice that of the center crotch portion. The pads are symmetrical about a longitudinal centerline axis therethrough. In other words, the pads can be symmetrically folded lengthwise. In this particular embodiment, the back ear portion may have a height defined by a cross-directional cut line that is shared by the next commonly oriented pad in the repeating pattern. Thus, all of the pads having the crotch portions oriented in one direction would have adjacent ears defined by a common cross-directional cut line. The oppositely oriented or nested pads have crotch portions nested against the ears of their respective adjacent pads. With this particular arrangement, the cut line defining the ears of adjacent commonly oriented pads corresponds to the longitudinal centerline of the pad nested therebetween.
In another embodiment of a generally T-shaped absorbent pad, the crotch portion has a first longitudinally extending section having a first width, this section diverging along lines into a longitudinally extending second section having a second greater width. With this embodiment, the pads are still symmetrical about their longitudinal centerline axis. The diverging lines between the first width section and the second width section have a center point through which the machine-direction centerline axis of the strip of web material passes. This line may be straight or sinusoidal. The sides of the crotch section along the first width and second greater width sections may be generally parallel.
In still further embodiments, the absorbent pads are defined with cross-directional cuts such that each pad has a longitudinal length equal to the cross-directional width of the strip of absorbent web material. In this embodiment, a single cross-directional cut line defines a common longitudinal side of adjacent nested pads. These pads may have a back ear portion with a center crotch portion extending longitudinally therefrom. An angle of divergence is defined at a cut line between the crotch portion and the ear portion that corresponds to the same angle for the immediately adjacent and oppositely oriented pad. This cut line may be generally straight or sinusoidal, and has a center point through which the machine-direction centerline axis of the strip of web material passes.
The method will be explained in greater detail below by reference to particular embodiments thereof.